Contemporary gas turbine engines incorporate an axial compressor section that is comprised of a plurality of airfoil sections, i.e. vanes, extending radially outwardly from a central axis of the gas turbine engine in a circular pattern, and rotatable about the central axis. Multiple circular patterns of rotor vanes are typically arranged sequentially in rows along the central axis. Between adjacent rows of rotor vanes there is also typically a set of vanes, also arranged in a circular pattern and extending radially relative to the central axis of the engine, differing from the rotor vanes in that these vanes do not rotate about the central axis of the turbine engine. These non-rotating vanes are commonly referred to as stator vanes, and each row thereof is commonly referred to as a stage. It is known to incorporate a plurality of rows of rotor vanes, as well as a plurality of rows of stator vanes, in an alternating pattern.
It is known to adjust the orientation of each stator vane about its central, radially extending, longitudinal axis to vary the angle of attack these stator vanes present to air flowing axially along the central axis of the engine and from the upstream rotating set of rotor vanes using an actuator. These variable stator vanes allow for the turbine engine to achieve air flow pressure characteristics for optimal operation in various modes of operation.
Various actuator configurations are known for achieving the aforementioned variable stator vane actuation. Each row of stator vanes, and particularly each vane thereof, is typically connected to a unison ring that is accessible from an exterior of a housing containing the rotor and stator vane rows. Rotation of this unison ring about the central axis of the engine results in the above described stator vane actuation. Each row of stator vanes has its own unison ring. A typical variable stator vane actuator thus manipulates multiple unison rings to govern the orientation of the variable stator vanes of each row of stator vanes. Examples of such actuators may be seen from inspection of U.S. Pat. Nos. 4,755,104, 5,549,448, 6,769,868, and 8,435,000, the entire teachings and disclosures of which are incorporated herein by reference thereto.
A common thread of such actuators, unfortunately, is that they are relatively complex in their construction, relatively large in size and weight, present a significant amount of wear points, and have high reactive loads. Indeed, U.S. Pat. No. 5,549,448 illustrates a conventional bell-crank style actuation arrangement. Such configurations are typically actuated by a linear actuator that is arranged and operates parallel to the central axis of the engine. This style is generally compact given the parallel arrangement of the linear actuator; however, it is also quite complex in its linkage arrangement as it requires multiple individual bell-crank mechanisms driven by a common master bell-crank mechanism, each of which presents a wear point and possible point of failure.
As another example, U.S. Pat. No. 8,435,000 illustrates a more contemporary torque-tube style actuation arrangement, wherein a rotary actuator, typically referred to as a torque tube, is arranged parallel to the central axis of the engine. A plurality of linkage arms extend from the torque tube and are connected respectively to each unison ring. An actuator acts upon the torque tube to rotate the same about its central axis to ultimately rotate the unison rings to achieve a desired stator vane orientation. This style is generally less complex than the bell-crank configuration described above. However, this configuration also utilizes a linear actuator that is arranged transverse to the central axis of the engine, and thus results in an undesirably large footprint within the engine space.
As such, there is a need in the art for a rotary actuator that has a reduced complexity, part count, number of wear points, and size.
The invention provides such a variable stator vane actuator. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.